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Question No. (1):
Put (√) tick for correct sentence and (χ) tick for
incorrect sentence and make the suitable modification: (20
degrees)
1-
The compass card of
quadrant compasses is divided into four quadrants of 90° each
(√)
2-
A magnetic pole
is a point on the surface of the earth where the lines of magnetic force
are horizontal. (vertical) (χ)
3-
A strike line
on a structure can be described as the intersection between an
imaginary vertical (horizontal) plane and the structure. (χ)
4-
An azimuth of S48°E
in the quadrant convention translates to 132° in the azimuthal
convention. (√)
5-
The true dip of a plane
is the steepest angle between the plane and a horizontal plane as
measured in a unique vertical plane. (√)
6- The attitude of a plane can be specified by its trend and plunge (strike/dip)
(χ).
7- The strike of a plane is the angle between
the strike line and true north and is measured in degrees with a compass (√).
8- A strike of N32°E is exactly the same as
a strike of S32°W (√).
9- An azimuth of N00°W in the quadrant convention translates
to 270° (360°) in the azimuthal convention (χ).
10- The magnitude of an apparent dip must always be greater (smaller)than
that of the true dip (χ).
11- The rake of a line (or
pitch) is the angle between the line and the vertical (horizontal)
as measured in the plane on which the line occurs (χ).
12- The intersection of the equatorial projection plane with
the sphere is called the primitive circle (√).
13- The pole to a plane is the straight line
perpendicular to the plane (√).
14- The fold hinge is the point of intersection
between the two limbs (√)
15- A dihedral angle is the angle between two planes
measured in a vertical (perpendicular) plane (χ).
16- The angle between a line and a plane is measured by
the angle between the line and the pole to plane
(its orthographic projection on that plane)
(χ).
17- A contour line on an equal-area plot
separates zones of the plot in which the densities of point data are different
(√)
18- Densities of point data are usually measured as a
percentage of the total number of points per 1% area of the stereogram (√)
19- To translate the numbers of points within each hexagon
into percentages of the total number of points, you have to use the
equation: (n / N) x (100) (√)
20- A plane of attitude 50°, N50°E must has a pole of
attitude 40°, S40°W (√).
Question No. (2): (10
degrees)
Compare
between each of the following (support your answer wit diagrams):
1- The quadrant and the azimuthal convention
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The quadrant convention
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the azimuthal
convention
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The range of possible direction
is divided into four quadrants (NE, SE, NW, and SW) of 90°
each, and the strike is specified by a given number of degrees east or west
of north.
-
A strike of N32°E
is read, "north thirty-two degrees east." Note that a strike of
N20°W is exactly the same as a strike of S20°E, because there is no need to
differentiate between the ends of a horizontal line.
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It is common practice to
specify strikes in the quadrant system with respect to north and south.
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the quadrant convention a
strike should always be specified by two digits, even if some of the digits are
0 (e.g., 05°).
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The quadrant is measured
either clockwise or counter clockwise from north or south
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the range of possible
directions on a horizontal plane is divided into 360°, with the direction of
due north being assigned a value of 000° or 360°
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Strike in the azimuthal convention can be
specified entirely by a number. For example, if the strike line points
exactly northeast, the strike is 045°.
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An azimuth of N00°W in the quadrant convention
translates to 000° in the azimuthal convention.
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Notice that the azimuthal
convention a strike should always be specified by three digits, even if some
of the digits are 0 (e.g., 056°).
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The azimuth is measured
clockwise from north
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2- b- diagram and p-diagram
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b- diagram
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p-diagram
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Every segment of a
cylindrically folded surface contains a line segment that is parallel to the
fold axis.
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Any two tangential planes
to the folded surface will intersect along a line that is parallel to the fold
axis.
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On an equal-area projection,
the great circles representing the attitudes of the folded surface at
different points on the fold should all intersect at the fold axis. This
point is called the b-axis.
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The p-diagram is an equal-area plot of the poles
to planes that are tangential to the folded surface.
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On a cylindrical fold,
each of the poles is perpendicular to the fold axis; thus, the poles are
parallel to a plane perpendicular to the fold axis.
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On an equal-area plot the
poles approximate a great-circle girdle, which is called the p-circle
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The pole to the p -circle is the p -axis and it represents the fold axis.
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The p -axis should coincide with the b-axis on a plot.
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